FrameTimeline: Optimize tracing information about frame start time

If the prediction state is expired but the actual start time is
available, prioritize the actual start time as the reference for the
actual timeline instead of using the actual end time.

Flag: EXEMPT. bug fix from external contributor

Signed-off-by: liuzhifu <liuzhifu@xiaomi.com>
(cherry picked from https://android-review.googlesource.com/q/commit:13eb5161b25da09feabfb9c4c89e6804da92056b)
Merged-In: I1646a159ab74b3d7918067e24c6e827bf6ae5b4e
Change-Id: I1646a159ab74b3d7918067e24c6e827bf6ae5b4e